Invisible Security Ink Based on Water‐Soluble Graphitic Carbon Nitride Quantum Dots

Abstract

Stimuli-responsive photoluminescent (PL) materials have been widely used as fluorescent ink for data security applications. However, traditional fluorescent inks are limited in maintaining the secrecy of information because the inks are usually visible by naked eyes either under ambient light or UV-light illumination. Here, we introduced metal-free water-soluble graphitic carbon nitride quantum dots (g-CNQDs) as invisible security ink for information coding, encryption, and decryption. The information written by the g-CNQDs is invisible in ambient light and UV light, but it can be readable by a fluorescence microplate reader. Moreover, the information can be encrypted and decrypted by using oxalic acid and sodium bicarbonate as encryption reagent and decryption reagent, respectively. Our findings provide new opportunities for high-level information coding and protection by using water-soluble g-CNQDs as invisible security ink.

Hot‐Tailoring of Carbon Nitride Dots with Redshifted Photoluminescence for Visual Double Text Encryption and Bioimaging

“…In addition, the writing showed good resistance to tap water, imitation sweat, and ethanol (see Figure S14), which suggests its potential to be worn. Compared with previous text encryption using CNDs with UV emission, the strategy used here would be more convenient . Therefore, the redshifted PL and other unique properties, that is, the highly sensitive and selective quenching specifically by Cu 2+ and the highly selective and efficient recovery by using EDTA, makes the as‐obtained CN450‐680(1+4)‐H 2 O a very promising agent for use in visual dual text encryption for high‐security applications.…”

“…By following this principle, the pioneering cleavage of bulk CN into carbon nitride dots (CNDs) with high photoluminescent quantum yield was achieved . However, due to strong quantum size effects, these CNDs emitted ultraviolet (UV) and even deep‐ultraviolet (DUV) light, which significantly restricted their biological applications in, for example, bioimaging, in which the potential damage to cells of ultraviolet light should not be overlooked. Notably, pioneering work on the surface modification of carbon nitride leading to improved dispersibility in aqueous and/or organic media has also been reported, thereby offering a solution .…”

Geheimtinten

“…Chinesischen Wissenschaftlern ist es kürzlich gelungen, eine High‐Tech‐Variante einer unsichtbaren Tinte zu entwickeln . Diese basiert auf Quantenpunkten, womit nanoskopische Häufchen eines Halbleitermaterials bezeichnet werden.…”

Secret Paper with Vinegar as an Invisible Security Ink and Fire as a Decryption Key for Information Protection

“…High‐level encryption techniques are of ever‐increasing importance for applications such as information protection, anti‐counterfeiting, and data storage . Photoluminescent (PL) materials, including organic dyes, quantum dots, and lanthanide‐doped materials, are investigated for security applications. PL materials are usually incorporated into a solvent to prepare security inks, which are compatible with printing techniques such as inkjet printing .…”